Silent myocardial ischemia: dimensions of the problem in patients with and without angina

Effect of trimetazidine on quality of life in elderly patients with ischemic dilated cardiomyopathy

INTRODUCTION

Elderly patients have an increased incidence of ischemic dilated cardiomyopathy, often related to diffuse coronary artery disease. Data have been cumulated to suggest that trimetazidine improves myocardial ischemia in patients with ischemic heart disease and improves left ventricular function in elderly patients with ischemic cardiomyopathy. The purpose of the present study was to assess the effects of trimetazidine in addition to standard cardiovascular therapy on left ventricular function and quality of life (QOL) parameters in elderly patients with ischemic heart disease and reduced left ventricular function.

METHODS

Patients were randomized to receive either trimetazidine (twice daily) or placebo (twice daily) in addition to standard therapy, and were evaluated at baseline and after 6 months.

RESULTS

Forty-seven patients completed the study (40 male, seven female; mean [+/-SD] age 78+/-3.4 years). Demographic data were comparable between the two groups with respect to sex, age, and race. At 6 months there was a significant improvement in the number of angina episodes per week in the trimetazidine group (-2.3+/-1, P=0.023). The overall assessment of QOL by a visual analog scale showed an improvement in patients randomized to trimetazidine at 6 months (from 4.1+/-0.6 to 6.4+/-0.8, P<0.01) and no changes in patients randomized to placebo (from 4.3+/-0.7 to 4.2+/-0.9, P>0.05). Physical QOL, evaluated by a MacNew Quality of Life After Myocardial Infarction questionnaire (MacNewQLMI), improved in patients randomized to trimetazidine but not in those allocated to placebo (32%+/-5% vs. -1%+/-3%, P<0.01). Similar results were obtained on social QOL evaluated by MacNewQLMI with trimetazidine compared with placebo (39%+/-4% vs. -2%+/-5%, P<0.01).

CONCLUSION

In elderly patients with ischemic heart disease and reduced ventricular function, trimetazidine improves clinical condition and QOL.

Risk factors related to the occurrence of silent myocardial ischemia in Mexicans

BACKGROUND

Silent myocardial ischemia is a growing world health problem. It has been related to factors that promote an increase in myocardial oxygen demand or affect coronary vasomotor tone. Coronary artery disease has shown an increasing trend in Mexico in this century.

HYPOTHESIS

The aim of the study was to estimate the strength of the association between some risk factors and the occurrence of silent myocardial ischemia.

METHODS

A cross-sectional study was conducted and 249 individuals were screened by 24-h Holter electrocardiogram. Silent myocardial ischemia was diagnosed in patients with painless transient ST-segment depression. All subjects were interviewed for coronary risk factors and total serum cholesterol was measured.

RESULTS

Silent ischemia was diagnosed in 115 patients (46%), who were older (59 +/- 9 vs. 57 +/- 11 years; p = 0.01). In a logistic regression analysis, a lower risk for silent ischemia was found in patients with thrombolysis [odds ratio (OR) 0.28; 95% confidence interval (CI 95%) 0.14-0.53], or those who followed their medical treatment (OR 0.16; CI 95% 0.04-0.68). The major risk factors were hypercholesterolemia (OR 1.6; CI 95% 0.9-2.9) and more severe coronary artery disease (OR 2.5; CI 95% 1.1-5.7).

CONCLUSIONS

Some coronary risk factors are related to silent ischemia. It is still important to diagnose this entity, but modification of its related risk factors should be kept in mind to diminish its occurrence and its severe consequences.

Reviewing myocardial silent ischemia: specific patient subgroups

Silent myocardial ischemia (SMI) is a relatively common, yet poorly understood, clinical entity. The most accurate means of detecting SMI and the precise treatment endpoints remain unclear. However, the presence of SMI correlates with the likelihood of future adverse cardiac events. Evidence suggests that patients at high risk of severe cardiac ischemia, even with the absence of symptoms, derive the greatest benefit from an aggressive diagnostic and therapeutic approach. This paper is giving a detailed review of SMI in regards to specific patient subgroups, i.e. populations with diabetes mellitus, hypertension, elderly patients, post-revascularization patients, women, the suggested screening procedures for each subgroup, as well as the emersion of new markers for the selection of high-risk patients for screening.

Diagnostic and prognostic value of Holter-detected ST-segment deviation in unselected patients with chest pain referred for coronary angiography: a long-term follow-up analysis

OBJECTIVE

To evaluate the diagnostic and prognostic significance of ST-segment deviation detected by ambulatory Holter monitoring in unselected chest pain patients referred for coronary angiography.

METHODS

Two hundred seventy-seven patients (71% were men) who underwent coronary angiography for evaluation of chest pain were studied with 24-h ambulatory Holter monitoring within 72 h of angiography. A lumen diameter reduction of > or = 50% was considered coronary artery disease. The ST-segment deviation was defined as > or = 1-mm deviation from the baseline lasting > or = 1 min separated by a minimum of 1 min. The patients were followed up for 65 +/- 21 months (mean +/- SD) for occurrences of death, myocardial infarction, hospitalization for unstable angina, and need for revascularization.

RESULTS

Of the 277 patients, 223 (80%) had coronary artery disease. The prevalence of coronary artery disease was not significantly different in patients with (43 of 48 patients; 90%) and without (180 of 229 patients; 79%) Holter-detected ST-segment deviation. The diagnostic accuracy of Holter-detected ST-segment deviation in predicting the presence of coronary artery disease was poor (33%), with a sensitivity of 19% and a specificity of 91%. The presence of Holter-detected ST-segment deviation was not predictive of future cardiac events or death.

CONCLUSION

The ST-segment changes detected on ambulatory Holter monitoring are of limited value in identifying coronary artery disease and predicting the future adverse cardiac events or death in unselected patients with chest pain.

Cardiac risk stratification of patients with symptomatic spinal stenosis

The leading cause of death in the perioperative period after noncardiac surgery is a cardiac event. As the number of lumbar surgeries performed in patients older than 65 years of age continues to increase, this patient population with neurogenic claudications is an at risk group for a cardiac event because of their age and associated cardiac risk factors. The authors attempted to document by means of cardiac chemical stress testing, the prevalence of silent ischemic cardiac disease in patients with neurogenic claudication who were candidates for elective lumbar surgery. Eleven of 140 patients (8%) had induced cardiac wall abnormalities on stress testing, indicating myocardial ischemia. The only risk factors associated with cardiac ischemia were smoking and history of heart disease. It is recommended that dobutamine stress echocardiography be performed in patients undergoing elective spinal surgery for symptomatic spinal stenosis if they have a history of previous heart disease, smoking, or both.

Detection of silent myocardial ischemia patients by the spatial velocity electrocardiogram

This study was designed to detect patients with type I silent myocardial ischemia (SMI) at rest by assessing the symmetry of the electrocardiographic (ECG) T wave using the spatial velocity electrocardiogram (SVECG). In this study, the ECG T waves in patients with SMI were symmetric compared with those in normal subjects, and the the c/a ratio in the SVECG-T wave as the index of degree of symmetry of the ECG T wave enabled us to diagnose 73% of these patients; the c/a ratio in the SVECG T wave was a useful index for detecting patients with type I SMI at rest.

Silent myocardial ischemia

The documentation of abnormalities related to myocardial ischemia, whether symptomatic or silent, is of central importance. Whenever this information is available, it should be used in the overall assessment of the patient at risk for adverse outcome. The level of concern for treatment of CAD should be based on the risk implications associated with the ischemia-related abnormalities detected during objective testing rather than on the presence or absence of pain. The exercise stress test is still the single most useful test to begin the evaluation of a patient with an analyzable ST segment. In persons suspected of having CAD, the detection of ischemic-type ST-segment depression, at a low workload (e.g., < 120 beats/min or < 6.5 METS) of > 2 mm magnitude or persisting for more than 6 min implies high risk for adverse outcome. Asymptomatic ischemia during everyday activities, detected by Holter monitoring, in the high-risk patient, most probably adds additional risk beyond the risk of an abnormal stress test alone. Left ventricular imaging by two-dimensional echocardiography, RNA, angiogram, vest, etc, showing an ejection fraction > or = 40%, reversible wall motion abnormalities in multiple regions and redistribution defects or a failure to increase ejection fraction during exercise even if the patient remains asymptomatic, also imply high risk. The presence of any of these abnormal findings, regardless of symptoms, should therefore prompt as high a degree of concern as with ischemia-related signals associated with pain. Thus any therapy chosen should be directed toward elimination of transient ischemia, not just relief of symptoms that may or may not be ischemia related. If this course is chosen, the efficacy of the therapeutic regimen and possible progression of CAD should be assessed with follow-up testing for ischemia. We believe that risk factor modification and aspirin should be considered for most, if not all, patients in whom ischemia, silent or symptomatic, is suspected or detected. If symptoms or ischemia suggesting low risk is present, anti-ischemic medical therapy may be considered, but follow-up is advised. If a high-risk ischemic signal, even without symptoms, is detected, medical therapy should be used to attempt to modify the signal. If the ischemic signal suggesting high risk persists despite medical therapy, revascularization should be considered. Until additional data from large clinical trials are available, this approach appears to have the greatest likelihood of modifying the adverse outcome of CAD.

Can we really justify the treatment of silent ischemia in 1992? No!

Since the advent of ambulatory ST-segment monitoring, it has been established that silent ischemia is common in patients with various coronary artery disease syndromes, and such silent episodes represent up to 80% of all ischemic episodes. It appears to be associated with an adverse prognosis when compared with similarly characterized patients without silent ischemia during daily life. Silent ischemia does not, however, bother the patients, by virtue of the fact that it is silent, and therefore treatment of such ischemia must be justified by an improved outlook for the patient, rather than symptom relief. There is no direct evidence to date that silent ischemia is associated with acute myocardial infarction or sudden cardiac death in a cause-and-effect relationship, or that reduction or eradication of silent ischemia will lead to an improved prognosis for the patient; indeed, we have been unable to demonstrate any significant improvement in outlook when using the various antianginal/antiischemic agents at our disposal. Until we can demonstrate a benefit to the patient by detecting and treating silent ischemia, we should not waste large resources attempting to eradicate something whose significance we do not understand.

Transient myocardial ischemia in hypertensive heart disease

This study determined whether episodes of myocardial ischemia occur in hypertensive patients with normal coronary angiograms. ST-segment analysis during 24-hour Holter electrocardiography was determined in 48 patients (24 men and 24 women, mean age 54.6 +/- 10.4 years) with essential arterial hypertension (systolic/diastolic blood pressure 189.7 +/- 29/99.5 +/- 15 mm Hg). The thickness of left ventricular posterior wall and septum were measured with echocardiography. Stenosis of coronary vessels were excluded on angiography in all patients. In 24 of 48 patients, 12.8 +/- 13.8 episodes of transient myocardial ischemia (ST-segment depression greater than or equal to 1 mm, duration of the episode greater than or equal to 1 minute) were observed. The duration of the episodes was 48.1 +/- 69.93 minutes and the maximal ST-segment depression was 1.91 +/- 0.82 mm. In 95% of the episodes the patients did not experience any angina pectoris. The degree of left ventricular wall thickness did not differ in hypertensive patients with and without transient myocardial ischemia (septum thickness 11 +/- 2 mm). It is concluded that transient myocardial ischemia often occurs in hypertensive patients. Thus, left ventricular hypertrophy does not appear to play any important role. The underlying cause appears to be the impaired coronary dilation capacity, i.e., vascular alterations.

Unstable angina

Unstable angina can manifest as an array of symptom complexes. In some patients, medical therapy will stabilize the episodes of angina, and only predismissal exercise testing or angiography (or both) will be necessary. At the other end of the spectrum are patients with rest angina or multiple episodes of silent ischemia who are refractory to medical therapy and experience undetected microinfarction. Most of these patients require immediate catheterization and subsequent intervention with intra-aortic balloon pulsation, percutaneous transluminal coronary angioplasty, or coronary artery bypass grafting. An entire spectrum of manifestations exists between these two extremes. One challenge during the 1990s will be better stratification of patients with unstable angina so that safe, efficient, cost-effective treatment strategies can be appropriately applied to all patients.

Transcardiac serotonin concentration is increased in selected patients with limiting angina and complex coronary lesion morphology

Serotonin is released by activated platelets and may act as a mediator to initiate or sustain certain unstable syndromes of ischemic heart disease in humans. To determine whether or not serotonin concentration increases across the coronary bed in patients with severe, limiting angina, we measured central aortic and coronary sinus serotonin concentrations by a sensitive radioenzymatic assay in 39 patients with coronary artery disease and 13 patients with minimal or no coronary artery lesions as detected by arteriography. Although no difference existed in the mean aortic or coronary sinus serotonin concentrations between these two groups, elevated coronary sinus serotonin concentrations were detected in 23% of those with coronary artery disease. The coronary sinus and aortic serotonin concentration difference was greater in patients with significant coronary artery disease (0.6 +/- 6.62 ng/ml) compared with patients without significant coronary artery disease (-5.6 +/- 10.32 ng/ml) (mean +/- SD) (p less than 0.05). Further analysis revealed that patients with eccentric, irregular coronary artery lesions or intraluminal filling defects had a significantly elevated coronary sinus and aortic serotonin difference (3.1 +/- 5.54 ng/ml) compared with those with smooth concentric lesions (-1.9 +/- 6.61 ng/ml) (p less than 0.02). These data suggest that serotonin is released into the coronary circulation of some patients with coronary artery disease, especially those with frequent angina and complex coronary lesions. Although serotonin may be released in some patients with coronary artery disease, the specific pathophysiologic role of serotonin in the development or perpetuation of certain coronary syndromes in humans remains to be determined.

Usefulness of ambulatory radionuclide monitoring of left ventricular function early after acute myocardial infarction for predicting residual myocardial ischemia

Ambulatory radionuclide monitoring of left ventricular function was performed with the nuclear Vest device in 35 patients early after acute myocardial infarction. Patients were evaluated during post-infarction treadmill, other activities that included mental stress and cold pressor challenge, and with stress thallium imaging and cardiac catheterization. Of the 35 patients evaluated, 14 had ischemic responses on treadmill testing and 21 had negative responses. By contrast, 20 had redistribution by thallium imaging suggesting ischemia. Vest studies demonstrated 56 responses suggestive of ischemia in 23 patients. Twenty-two occurred during exercise and 13 with mental stress. Seventy-five percent were silent and only 39% had associated electrocardiographic changes. Vest responses were compared in patients whose thallium scan was indicative of ischemia (thallium-positive) and those without ischemia (thallium-negative). Ejection fraction was higher in the thallium-positive group (0.52 +/- 0.11), as compared with thallium-negative patients (0.44 +/- 0.1). With exercise, ejection fraction decreased for the thallium-positive patients from 0.52 +/- 0.11 to 0.40 +/- 0.09 at peak exercise. For thallium-negative patients, ejection fraction changes were not significant. During mental stress, ejection fraction decreased from 0.51 +/- 0.11 to 0.45 +/- 0.12 for thallium-positive patients while thallium-negative patients were unchanged. Vest-measured decreases in ejection fraction of greater than or equal to 5 units during exercise were highly sensitive (90%), specific (73%) and predictive (82%) of a positive thallium scan. The same response for mental stress was specific (87%) and predictive (85%) of a positive scan result.(ABSTRACT TRUNCATED AT 250 WORDS)

Silent myocardial ischaemia in chronic stable angina: a study of its frequency and characteristics in 150 patients

One hundred and fifty unselected patients with documented coronary artery disease were studied to establish the frequency and characteristics of silent myocardial ischaemia. Patients underwent ambulatory ST segment monitoring off all routine antianginal treatment (total 6264 hours) and exercise testing (n = 146). Ninety one patients (61%) had a total of 598 episodes of significant ST segment change, of which 446 (75%) were asymptomatic. Twenty seven patients (18%) had only painless episodes; 14 (9%) patients only painful episodes; 50 patients (33%) had both painless and painful episodes. The mean number of ST segment changes per day was 2.58 (1.95 silent); however, 11 patients (7%) had 50% of all silent episodes, and 48 patients (32%) had 91% of all silent episodes. Fifty nine patients (39%) had no ST segment changes on ambulatory monitoring, and 73 patients (49%) had no evidence of silent ischaemia. Episodes of silent ischaemia occurred with a similar circadian distribution to that of painful ischaemia, predominantly between 0730 and 1930. There was a similar mean rise in heart rate at the onset of both silent and painful episodes of ischaemia. Silent ischaemia was significantly more frequent in patients with three vessel disease than in those with single vessel disease, and was also significantly related to both time to 1 mm ST depression and maximal exercise duration on exercise testing. There was a highly significant relation between the mean number and duration of episodes of silent ischaemia in patients with positive exercise tests when compared with those with negative tests. No episode of ventricular tachycardia was recorded in association with silent ischaemic change.

Circadian variation of total ischaemic burden and its alteration with anti-anginal agents

6264 hours of ambulatory ST segment monitoring of 150 unselected patients with proven coronary artery disease, who were off all routine anti-anginal treatments, showed 598 ischaemic episodes, of which 446 (75%) were silent (symptom-free). Most (68%) ischaemic episodes occurred between 0730 and 1930, with a peak in the morning and a lesser peak in the evening. Two subgroups were studied further in double-blind controlled trials: 33 patients had a total of 1313 hours of ST segment monitoring while treated with nifedipine; and 41 patients a total of 1581 hours while treated with atenolol. Nifedipine did not alter the circadian pattern of ischaemic episodes; atenolol abolished the morning peak, and the peak incidence of ischaemia then occurred in the evening. Circadian patterns for total duration of ischaemic episodes corresponded closely to those of episodes of ischaemia, and were similarly altered by treatment. The circadian pattern of silent ischaemic episodes and their total duration were very similar to those of total ischaemia for the group as a whole and the different subgroups. This circadian distribution of ischaemic episodes and the observed changes with treatment resemble the reported circadian variation of acute myocardial infarction and sudden death.

Silent myocardial ischemia: an update

Silent myocardial ischemia is diagnosed by several different techniques and has been documented in all the anginal syndromes. In addition to other factors, its presence may be related to increased pain threshold and increased pain tolerance. Although some patients with painless ischemia may have less extensive coronary artery disease, cumulative evidence indicates that silent myocardial ischemia does not necessarily signify a lesser degree of cardiac ischemia or a less severe coronary abnormality. As judged by ambulatory monitoring studies, it shows circadian variation; occurs more frequently than symptomatic ischemia; and appears to depend, in large part, on activation of the sympathetic nervous system. Frequent silent ischemic events during ambulatory monitoring are worrisome because they reflect the disease "activity" of single or multiple coronary atherosclerotic lesions. Thus, there may be a direct association between the severity of ischemia seen during Holter monitoring, the extent of underlying coronary artery disease or disease activity, and prognosis. When diagnosed by exercise testing, silent myocardial ischemia may be associated with significant coronary involvement. In this regard, patients with three vessel coronary disease, impaired left ventricular function, and silent ischemia during stress testing should benefit from coronary revascularization. Compared with symptomatic patients, other evidence suggests that patients with exercise-induced asymptomatic ischemia have at least the same or perhaps even a worse outlook; this may be related to the lack of symptoms that would prompt evaluation and therapy. Awareness of the possibility of silent myocardial ischemia and use of commonly available tests, both to establish its presence and severity and to guide treatment, are emerging as new clinical goals. Further data, however, are necessary to determine how vigorously this should be pursued in different patient subgroups. In association with unstable angina or post-myocardial infarction, the added risk of silent myocardial ischemia warrants a more aggressive approach.

Labetalol in normotensive patients with angina pectoris

Labetalol, an alpha-beta-blocker, has been shown to have vasodilating as well as beta-blocking properties. From the theoretical point of view such a drug is likely to be beneficial in the treatment of angina pectoris. There are very few studies investigating the effects of labetalol in normotensive patients with angina pectoris. The three major controlled trials that have been published show that labetalol reduces angina frequency and prolongs exercise duration. In one study the effects of labetalol in anginal subjects using ambulatory monitoring was performed and showed a reduction in silent ischemia as well as a reduction in angina pectoris. Thus labetalol would appear to be an effective antianginal agent. Further studies are necessary to determine if the anti-anginal effect is entirely due to the beta-receptor-blocking activity of the drug or whether labetalol's vasodilating property has important additional benefit.

Antianginal drug therapy for silent myocardial ischemia

Many of the available nitrate preparations, beta-adrenergic blockers, and calcium antagonists appear to be useful in patients with painful and silent ischemic episodes detected on the ECG (Table 1). More controlled studies need to be done using standardized methodologies for assessing silent myocardial ischemia, to evaluate and compare the different antianginal medications. It is fortunate, however, that the nitrates, beta-blockers, and calcium antagonists, used alone and in combination, appear to have favorable effects not only on painful ischemic episodes but also on those ischemic episodes not associated with pain.

Calcium antagonists for Prinzmetal's variant angina, unstable angina and silent myocardial ischemia: therapeutic tool and probe for identification of pathophysiologic mechanisms

The calcium antagonists provide a unique tool to reduce myocardial oxygen demand and prevent increases in coronary vasomotor tone. For patients with Prinzmetal's variant angina, diltiazem, nifedipine and verapamil are extremely effective in preventing episodes of coronary vasospasm and symptoms of ischemia. Unstable angina pectoris is a more complex pathophysiologic syndrome with episodes of ischemia due to increases in coronary vasomotor tone, intermittent platelet aggregation or alterations in the underlying atherosclerotic plaque. Each of the calcium antagonists is effective as monotherapy in decreasing the frequency of angina at rest. Nifedipine is the only calcium antagonist that has been studied in a combination regimen with beta blockers and nitrates for patients with unstable angina, and control of angina is better with the combination regimen than with either form of therapy alone. Although symptoms of myocardial ischemia in unstable angina are reduced by calcium antagonists, these agents do not seem to decrease the incidence of adverse outcomes. Antiplatelet therapy appears to improve morbidity and mortality in patients with unstable angina, suggesting that thrombus formation may play a central role in that disorder. Episodes of silent or asymptomatic myocardial ischemia, identified by ST-segment monitoring, occur in a variety of disorders of coronary disease. Among patients with Prinzmetal's variant angina and unstable angina, episodes of silent ischemia appear to be as frequent as episodes of angina and the calcium antagonists are effective in decreasing episodes of ischemia regardless of the presence or absence of symptoms. Persisting episodes of silent ischemia among patients with unstable angina despite maximal medical therapy identify patients at high risk for an early unfavorable outcome. Among patients with stable exertional angina, episodes of silent ischemia may be up to 5 times as frequent as episodes of angina, and may be due to increases in coronary vasomotor tone, transient platelet aggregation or increases in myocardial oxygen demand. Preliminary experience suggests that calcium antagonists and beta blockers are effective in decreasing episodes of silent ischemia in patients with stable exertional angina and that a combination regimen may be more effective than either form of therapy alone.